Aluminum soaps of mixed iso-octoic acids as gelling agents for liquid hydrocarbons



1': I '1 ALUMINUM SOAPSg ISO- OCTOIC ACIDS AS GELLING AGENTS FOR LIQUID HYDRO- CARBONS Leonard Cohen, Baltimore, Md.

No Drawing. Application November 1, 1954,

Serial No.4 66,242 v s Claims. 01.444

(Granted under Title 35, U. S. Code (1952), sec. 266) The invention described herein 3 may be manufactured and usedby orfor the Government of the United States ofAmerica-for governmental purposes without the pay-'-:

ment-tome of any royalty thereon.

This inventiorrrelates to aluminum soap of mixed isooctoic acids. More particularly, it relates to the alumi-, num di-acid soap of mixed iso-octolc acids. These soapshavea multitudeofrusesand;haveparticular utility as thickening-.agentsfor liquid hydrocarbons. Thus, when-' these soaps are mixed- .with hydrocarbon fuels such r1 as motor gasoline, they serve to produce the jellied gaso. line used in flame throwers andfire bombs.

The mixed iso-octoiciacids' from which these soaps: aremade are obtained by ,the oxidation ofiso-octyl alcohols; the 1atter-in-turn-zbeing produced from mixed hep-, tenes by anoxo processreaction. The'acids are largely 5, 6 and-Tcarbon atoms in, length-withresulting 3, 2 and 1 methyl-group substituentsonthecarbon chainrespectively. The 6 and 7 carbon atom chains are usually present in the: greater proportion.

A disclosure of the x0 process for preparing oxidation products from olefins together with utility for these products appears in U. S. Patent;No. 2,553,364.

The aluminum di-acid-soap is produced by reacting an aqueoussodium soap solution of the acid containing approximately 50% excess caustic, with an aqueous solution ofan inorganic aluminum-soap such as aluminum sulfate. The resulting-insoluble-hydroxyaluminum soap is filtered and washed free of by-product salts and dried.

Example Dissolve 43 grams of C. P. sodium hydroxide in 850 ml. of water. Add 100 gram of mixed iso-octoic acids (neutral equivalent=143.5) and cool to room temperature bystirring. Slowly add 342 ml. of aluminum sulfate solution containing 137 grams of Al2(SO4)3l8 H2O, (iron free), in a fine stream with good agitation to precipitate the aluminum soap. The aluminum soap is filtered and washed free of sulfate ion as indicated by barium chloride test solution. The soap is first dried by exposure to room atmosphere over phosphorous pentoxide in a desiccator.

The aluminum di-acid soap is precipitated in accordance with the following simplified equations:

Some mono-acid soap may precipitate concurrently in accordance with the following equation:

Because of hydrolysis the tri-acid soap AIR: does not form, and acid in excess of that required remains as much adsorbed on the di-acid soap as indicated in the following equation:

In the above equations HR denotes the mixed iso-octoic acids.

The dried granular aluminum soaps when added to liquid hydrocarbons create visco-elastic gels, the consistencies of which will vary with the concentration of thick ening agent employed. Such gels have been prepared in concentrations ranging from 1.0% to 4.0% by Weight of salt. The gels are useful in fire bombs as 'well as in portable and mechanical flame throwers. The, percentage of salt used, largely determines the consistency of the gel and accordingly the use to which it is put; Gel consistencies are to a lesser extent dependent upon the nature of the gasoline or hydrocarbon blend used as well as the mixing and storage conditions of the gel;

One method of determining the characteristic of a gel is by means of Gardner consistencies. These are atype of viscosity measurement and are described --fully in JAN-I7 11, 16 December 1948, National Military Establishment Specification. Incendiary Oils, Consistency of; Test Procedures. Section: Mobilometer Methods.

Such Gardner readings will vary from 25 for a 1% gel to about 675 for a 4% gel. Typical Gardner readings of a gel made with a hydrocarbon blend consisting of 18% benzene, 20% cyclohexane, 57% n-heptane and5% These gels are prepared by adding the required amount of soap to the test solvent and mechanically stirring. When the soap particles have solvated andswollen sufficiently, the vortex will close around the stirrer shaft and the mixture can then be stored without settling, The

Ga'rdner consistencies were determined after storage for about 24 hours at room temperature. Similar gels were made using ordinary motor gasoline in place of the hydrocarbon mixture previously referred to.

Using from 2 to 3% of soap, the readings were as follows:

Gardner Consistency, grams/ sec.

Percent Soap in Gasoline These Gardner consistencies serve as an indicator of the physical properties of the gel and therefore the utility for which they are suitable.

Since the characteristics of a gel suitable for a portable flame thrower differs from that required in a fire bomb as well as from that required in a mechanical flame thrower, tests were made of various gels to determine their suitability in each case. In tests with a portable flame thrower, gels were prepared from regular motor gasoline and including 1.5%, 2.0% and 2.5% aluminum salts by weight. The mixtures were stirred mechanically for 25 minutes at ambient temperature and aged about 24 hours before firing. Gardner consistencies of the fuels Patented Sept. 20, 1955' were determined at. thetime of firing. Results of these tests are tabulated as shown below:

In further tests with portable-flame throwers,-it was found that gels having -a 1.8 content of-aluminum salts were optimum in performance and gave a range of about 70 yards.

It is obvious that a formulation for this purpose is acompromise which must'take'into' consideration the type of flame desired as'well as the range and ignition properties 'of the gel.

Tests were also made'on the gels of the present invention for service as firebomb fuels. In this instance a heavier gel may beusccl since there isno need to maintain a viscosity suitable'forpassage through a nozzle as in a flame thrower. In this instance, 100 gallons of gasoline were made into a gel using 4% soap concentration. A fire bomb was filled with this fuel and released from a plane at a speed of '200 miles per hour from an altitude of 100 feet. The following results were noted:

Ignitiongood Fireball duration3.5 seconds Residual burning time-41 min., 30 seconds Percent unburnt gel2 to 5% Area covered-42 x 130 yds.

Other tests on fire bomb fuels showed that soap concentrations of between 3.5% and 4.0% were practical. As in the case of portable flame throwers, the composition of-a gel to be used'in'fire bombs must likewise be a compromise, including such factors as burning time, area covered, ability to stick to objects and other factors.

Tests werealso made 'of'the fuel in mechanized flame throwers and it was found that soap concentrations simi-' lar to thoseused' in fir'e bombs were'suitable. Concentrationof 3.75% was found to be optimum.

In addition to the uses indicated, these gels have other military applications such as filling for land mines and other structures calculated to impede enemy operations.

In applications such as fire bombs and land mines, soap concentrations in the vicinity of 4% are customarily employed although it is to be understood that this is not a limiting concentration and percentages up to 5 and 6% may sometimes be desirable for these applications.

Thisapplication is a continuation in-partof applica tion Serial-No. 321,747 filed November 20, 1952'.

I claim:

1. A method of gelling a liquid hydrocarbon which comprises agitating a mixture of a liquid hydrocarbon fraction with from -l% to 4% by weight of an aluminum mono and di-acid soap ofm'ixed' iso-octoic acids.

2. A method in'accordance with claim 1 wherein the hydrocarbon fraction is motor gasoline.

3. Amethod inaccordance with'clainr-l'wherein' the mixed iso-octoic acids comprise principally methyl heptoic dimethyl hexoic and trimethyl pentoic acids."

4. A method of producing-an incendiary gel which" comprises agitating-a mixture of a liquidhydrocarbon fraction and from about 1% to ab'o'ut4% by-weightof' an aluminum diacid soap-of a mixture'of'acids comprising principally methyl heptoic,- dimethyl-hexoicand tri methyl pentoic acids.

5. A gelled hydrocarbonconsisting-essentially ofan intimate-mixture of 1% to 4% of an aluminum m'on'o' and di-acid soap of mixed iso-octoic'acidsand-a -liquid hydrocarbon fraction. V

6. A composition in accordance with' claim' 5 'wh'erein* the liquid hydrocarbon"fraction' is motor *ga'solin'e.

7. A composition in accordance with claim' 5 wherein the mixed iso-octoic acids'comprise' principally martyr heptoic, dimethyl -hexoic and trimethyl pentoic acids.

8'. A composition inaccordance'with claim-'7 wherein the liquid hydrocarbon'fraction'isrrfotor gasoline? References Cited in the-file of this patent- UNITED 'STATES PATENTS Mason Aug. 11, 1953 

1. A METHOD OF GELLING A LIQUID HYDROCARBON WHICH COMPRISES AGITATING A MIXTURE OF A LIQUID HYDROCARBON FRACTION WITH FROM 1% TO 4% BY WEIGHT OF AN ALUMINUM MONO AND DI-ACID SOAP OF MIXTURE ISO-OCTOIC ACIDS. 